Spring hinge mounting for sound recording and reproducing heads



THOMPSON ET AL 2,369,087

SPRING HINGE MOUNTING FOR SOUND RECORDING AND REPRODUCING HEADS Filed June 25, 1943 2 Sheets-Sheet 1 i INVEN 5 I CO HO ON w; 'T- LETQvSE ATTORNEY Patented Feb. 6, 1945 SPRING HINGE MOUNTING FOR SOUN RECORDING AND REPRODUCING HEADS Lincoln Thompson, Cheshire, and Robert .L.

Stone, Orange, Conn., assignors toThe Soundscriber Corporation, New Haven, Conn, a corporation of Connecticut Application June 25, 1943, Serial No. 492,246 I 11 Claims.

This invention relates to improvements in dietating machines, andmore particularly to a novel form of stiff spring hinge mounting for the re-,

Fig. 6 is a plan view of still another modified form of spring hinge constructed of interleaved ords of the type disclosed in Reissue Patent 22,183,

issued September 22, 1942, to Lincoln Thompson, on an application-filed December 17, 1941, entitled Apparatus for recording sound on thin disks. It also constitutes an improvement over the mechanism disclosed in our prior Patent 2,240,321, issued April 29, 1941, entitled Tra'nscribing machine.

The present application is a continuation in part of our prior application S. N. 388,956, filed April 17, 1941, entitled Stepback mechanism for honograph tra'nscribers, which matured into Patent No. 2,323,257, dated June 29, 1943.

In recording and reproducing machines, it is desirable that the stylus heads of the recording and reproducing apparatus shall be flexible in a vertical direction but free from lateral play, and it is the main object of the present invention to provide a novel hinge mounting for such heads which will accomplish this purpose.

A further object of the present invention is to provide an improved mechanism of the above nature which will be relatively inexpensive to manufacture, simple in construction, compact, ornamental in appearance and very efficient and durable in use.

With these and other objects in view, there have been illustrated in the accompanying drawings several forms in which the invention may be con- I veniently embodied in practice.

In the drawings:

Fig. 1 is a perspective view of a dictating machine employing the improved mountings for supporting the recording and reproducing heads on their respective arms.

Fig. 2 is a top plan view, on a larger scale, of the reproducing arm and its associated pickup head showing the improved spring hinge connection therebetween for permitting vertical flexibility without lateral play.

Fig. 3 is a side view, on a still larger scale, of the front portion of same as it appears in operating position resting upon a disk record.

Fig. 4 is a plan view of a modified form of flat leaf spring hinge, also embodying the invention. Fig. 5 is a similar plan view of another modified form of leaf spring hinge which is provided with a central longitudinal slot to enhance the vertical flexibility thereof.

rubber and fabric and also having a longitudinal central slot.

Fig. 7 is a transverse sectional viewof thesame, taken along the line 1-'| of Fig. 6-.

Fig. 8 is a side view, partly in section, of the recording arm and head shown in Fig. 1, illustrating the leaf spring hinge which connects the base of said head to the base of said arm, and also showing the short limiting guard-plate mounted upon the top of said arm for engaging the rear end of the recording head. v

Fig. 9 is a side view, partly in section, of a modified form of a pickup head similar to Fig. 3, and showing an elongated guard pla'te rigidly secured to the top of the pickup arm and having its unsupported forward end lying slightly'a'bove the top of said head. 7

Fig. 10 is a side view, partly in'section, showing the pivotal mounting ofthe reproducer arm,

One advantage ofthe use of the improved spring hinge connection of the present invention is that side play between the recording'and reproducing'arms and their respective heads is 4 almost entirely avoided. This isof. the utmost importance in producing accurate recordings on a disk record and also in insuring an accurate and uniform amount of backspacing in a transcriber where a stepback mechanism is employed playing back portions of the record.

Referring now to the drawings wherein like reference numerals designate like parts throughout the several views, the numeral it indicates a. rectangular cabinet overwhich a turntable II is adapted to be driven at constant speed by a suitable electric motor (not shown). The tumtable II is provided with a spindle I2 having a square top which serves to centralize a thin record tablet l3 mounted upon the turntable l I.

Provision is also made of a recording arm I! 'which is mounted to rotate on a vertical shaft Ha, said arm being caused to travel at constant angular speed across the record l3 by suitable feed mechanism driven by the motor.

Upon the free end of the recording arm It, provision is made of a recording head l5, spaced a short distance from said arm l4, and connected I thereto by means of a thin resilientleaf spring hinge l6 having vertical flexibility, but being quite stiff horizontally to prevent lateral play.

The recording head I5 is adapted to beheld upwardly by means of a pair of short upstanding pins I1 and I8 connected together by an elongated counterbalancing small coil. spring l9.

for'

'I'hespring hinge -l l is preferably made rectangularin shape, and is preferably providedwith- I recording head 15.-

eight 'ap'ertures2ll (seeFlg; 8) to receive a like number of rivets 2-l.for securing the ends of said I spring-hinge rigidly to therecording-arm l4 and A reproducing arm *22 isalso provided,'and, as v shown in Figs. 1 to 3, is mounted to swing in a horizontal plane when the machine is level on a vertical shaft 22a (see Fig. which is sup-;

ported by a .U-shaped bearing bracket 23 mounted upo'n the top of the cabinet Ill. As clearly shown' 'in'Fig'ul, the reproducing arm 22 is provided with:

a rearwardly extending upwardlyofiset arm 24? carrying-a cylindrical counterweight 25 at its rearend. y

Provision is also made of a light wire tracking spring 26 extending upwardly from the rear of the bracket 23 andextending loosely through a small aperture 21 in the upper portion of the ofiset arm 24 so as to'provide a limited amount I of backlash;

The spring 26serves to compensate for or counteract the lateral component of stylus fric-.

'tion on the record tablet-tending to dislocate'it.

Itis loose in the aperture 21 so that the arm 22 may be swung a short-distance either side of its central or neutral sector before-the spring will, engage said am. When the backlash is taken, up, however, the spring 26 will oppose the lateral component of stylus friction with a forceincreasingapproximately in accordance with the increase of the angle between the reproducer arm 22 and the centralsectorn The operationof a similar compensating device is fully described in Patent No. 2,316,637 to Lincoln Thompson, issued April 13; 1943.

A pickup head 28 is piv'otally connected in spaced relation to the forward end of the reproducingarm '22 by-means of a thinrectangular leaf spring hing 29 similar. to the :hinge' l6 previously described Provision is also made of. a

pair of upstanding pins 30 and-3| mounted on the pickuphead 28 andreproducing arm'22 respectively, and connected.by:a counterbalancingr v wire :coil spring 32, similar to the spring IS.

The springhinge 29 is provided with eight apertures-33 for receiving a like'number of rivets 34, by means of which said hinge is connected to the upper portions of the reproducing arm 22 and pickup head 26(see Figs. 1-2-3).

' In the modified form of spring hinge shown i Fig. 4 provision is made of a resilient rectangular plate 35 having two apertures 36 and-31 at one end, a single aperture 38 at the other end, and an intermediate aperture 39 on one side of said plate."

This. :form-ofhinge'is employed when a somewhat less. resilient and 1 a stiffer construction is desireds a In :the modifiedform of spring hinge shown in Fig. 5. a resilient rectangular plate 40, similar to the plates |-6,=29 and '35, is provided, having two fabric having a central canvas sheet 52, and a pairofoverlying and underlying rubber layers 52a and 52bzrespectively.

Fig. 8 shows how the hinge plate l6 is-secured 'to'the bottom member 53 of the recording arm I 4 and'the bottom member54 of the recording head l5 respectively. The swinging movement of the head I5is limited by means of a short guard strip 55 secured by means of rivets 56 and 51 upon the top of the recording arm l4. The free end of the guard strip 55v extends forwardly into the space between the recording arm l4 and the rear surface 51 of the recording head l5, and thus serves to limit theamount of upward swinging of said head, as shown in dotted lines.

In the modified form of the invention shown in Fig. 9 a reproducing arm 58 is illustrated which is provided with a resilient hinge plate 59 connected with a pickup head 60 by means of two pairs of rivets 6| and 62 respectively, and provision is also made on the top of the arm 58 of an elongated resilient guard strip 63 rigidly secured at its rear end to the recording arm 58 by means of a plurality of rivets 64. The forward end 65-of the guard strip 63 is slightly raised above the pickup head 60 and serves to limit the upward flexing of said head as shown in dotted lines in Fig. 9. While there have been disclosed in this speci- =fication several forms in which the invention may a resilient leaf spring hing for connecting said arm to said head, said hinge being flexible vertically but not horizontally.

2. In a phonograph, a rigid arm mounted to swing over a sound record. a stylus head, a spring hinge havin no lateral flexibility connecting said head with said arm, and means connected to said sets of apertures 4l-and 42, Hand, atthe .ends thereof, and having an intermediate aperture 45 on one side. The plate 40 1s also providedwith alongitudinal central slot 45a--toincrease the vertical flexibility of said hinge'.-

' In the modified form-of the invention shown in Figs. 6 and 7, a vertically flexible hinge plate 46 is employed, which is also rectangular inshape and is provided with four corner apertures .41, 48, 49,: 505* The plate 46 is also provided-with a.

central slot,.5l to' increase the vertical flexibility thereof. The plate 46 is constructed of a com-.

bination oi-three interleaved layers'ofrubber and.

arm to counterbalance the weight of said head.

3. In a phonograph, a rigid supporting arm mounted to, swing upon a vertical axis over a rotating disk record, a stylus-carrying head, and a short thin leaf spring hinge connected rigidly at its ends to said arm and said head respectively a to provide a flexible connection therebetween,

whereby said head will be permitted to yield freely in a vertical directionbut will have substantially no lateral yieldability.

4. In a phonograph, a recording arm mounted to swing upon a vertical axis over a rotating disk record, a stylus-carrying recording head, a short thin resilient leaf spring hinge rigidly connected at its ends to the bottom portions'of said recording arm and said recording head respectively,

whereby said head will be permitted to yield freely in a vertical direction, but will have no lateral yieldability.

5. In a phonograph, a reproducer armmounted to swing upon a vertical axis over a rotating disk record, a pickup head, and a thin resilient spring hinge rigidly connected at its ends to the top portions of said reproducing arm and said pickup head respectively, whereby said pickup head will be permitted to yield freely vertically, but will have substantially no lateral yieldability.

6. The invention as defined in claim 3, in which said supporting arm and said stylus-carryinghead are each provided with 'an upstanding pin, and an elongated coil spring connected to said pins to counterbalance the weight of said head.

7. The invention as. defined in claim 3, in which said leaf spring hinge comprises a laminated sheet of fabric and rubber.

8. The invention as set forth in claim 3, in which said leaf spring comprises a central sheet of canvas, an overlying sheet of rubber, and an underlying sheet of rubber.

' 9. In a phonograph, a recording arm mounted to swing upon a vertical axis over a rotating disk record, a recording head, a thin resilient leaf spring hinge rigidly connected to the bottom portions of said recording arm and said recording head respectively, and a short flat guard plate attached to the top of said recording arm for engaging the rear surface of said recording head to limit the upward flexing thereof.

10. In a phonograph, a reproducing arm mounted to swing upon a vertical axis over a rotating disk record, a pickup head, a spring plate hinge rigidly secured at its ends to the upper portions of said reproducing arm and said pickup head respectively, and an elongated guard plate having its rear end rigidly secured on the top surface of said reproducing arm and having its forward end unsupported and raised slightly above the upper surface of the rear portion of said pickup head to limit the upward flexing thereof.

11. The invention as defined in claim 3, in which said leaf spring hinge comprises a thin rectangular sheet of resilient material and is provided with a narrow longitudinal slot therein to enhance the vertical flexibility thereof LINCOLN THOMPSON. ROBERT L. STONE. 

